The objective of this study is to investigate the effects of various growth factors on stimulation of bone formation. One particular protein of interest is Osteoblastic Specific Factor, (OSF-2). OSF-2 is expressed in osteoblasts in a highly specific manner. OSF-2 shows limited sequence homology with fasciclin I, a cell adhesion protein expressed in insect nerve cells. It is postulated that OSF-2 might play some role in the cell to cell communication in bone. However, there are limited studies on the function of OSF-2 in bone formation. Aim I of this study is to examine the role of OSF-2 in promoting osteogenesis. Aim I consists, (l)Expression of recombinant OSF-2 in mammalian cells. (2)Raise monoclonal and polyclonal antibodies against recombinant OSF-2 protein. (3)Mitogenesis, differentiation, and matrix synthesis of osteoblasts will be studied using MTS assay, Alkaline Phosphatase Assay, Osteocalcin Assay, and Western Blotting analysis. Cells used in this study include Osteosarcoma cell line (MG63), and Osteoblast-like cells obtained from fetal bovine bone. Aim II: Analyze synergistic interactions between OSF-2, VEGF, and other growth factor (TGF-, PDGF-BB, bFGF) on the regulation of bone growth and differentiation in the in Vitro cell assay described above. If synergistic effect is observed between two of the growth factors, induced expression of other genes can be measured by ELISA or PCR. If syergism is confirmed, a hybrid molecule consisting of for example, an OSF-2 moiety linked to a VEGF moiety can be created. Upon expession, the hybrid molecules can be tested in the experiments in Aim II, m, & IV. Aim III: Investigate synergistic interaction between OSF-2, VEGF, and growth factors on the regulation of bone formation in vivo. This assay involves implanting a mixture of proteins beneath the skin of mice using a collagen carrier. The activities of bone formation can be measured by assays mentioned above. Aim IV will focus on the in vivo study of healing around dental implants using the combination of OSF-2, VEGF, and other growth fac tors. The animal models for evaluating the bone-implant interface in this study will be Foxhounds dog model. The combination of OSF-2, VEGF, and growth factors are placed in endosseous implants, which are surgically placed in dogs three month following extraction of their mandibular dentition. The dogs will be sacrificed at established time periods and healing around the implants will be studied histomorphometrically. This study is important in investigating the effects of OSF-2 and other growth factors in bone formation. Synergistic effect in osteogenesis will be examined and this may lead to the creation of novel hybrid molecules that has enhanced biological activities. The use of these proteins and growth factors, individually, or in combination in dental implants may improve the bone-implant interface and increase stability of dental implants in poor bone quality.